Benjamin Franklin put it this way: “For want of a nail, the shoe was lost; for want of a shoe, the horse was lost; and for want of a horse, the rider was lost, being overtaken and slain by the enemy, all for want of care about a horseshoe nail.”

The clock is ticking on its critical labor shortage program, which allows retired teachers and other staff to return to work in special education, mathematics and other subjects where they are needed.

But some of these retired staffers must decide by today whether to take big pay cuts to stay in the program or return to retirement.

The numbers are not big, 129 of the district’s 18,000 teachers.

But hanging in the balance, the teachers union says, is whether some struggling schools will have enough teacher talent to help meet the complex benchmarks of the federal No Child Left Behind Act.

And whether those benchmarks are met may determine whether other teachers are kept at a school or transferred to other schools, or even whether a school is taken over by state officials.

There are obvious advantages to the School District in hiring a retired person when no other qualified person is available. A retired teacher likely has more credentials and experience than a substitute would.

Teachers coming out of retirement not only keep receiving pensions while working, but can also draw salaries, sometimes more than doubling their income.

Salary and pension rules are complex, and individual situations vary. Typically, a teacher retired after 30 years receives a $54,000 annual pension. If the teacher returns to the classroom, he or she can also collect a $60,000 salary. Some would call this double dipping.

Cynthia Sell, a district spokeswoman, said cutting back the program is not about money, but about state law, which defines rules that govern the number of teachers the district can employ under the program.

The number of retired teachers eligible for pension and pay slid from more than 250 in 2007 to 129 last school year, according to School District figures.

Under state rules, 60 teachers can collect both incomes this school year, meaning 69 face reduced pay or a return to retirement.

Why worry about such a small group of excluded teachers?

Rob Benson, a vice president of the Clark County Education Association, said that group has an outsize influence on how schools are evaluated under the federal law and that an exodus would hurt schools.

Of the excluded group, 30 are special education teachers.

Benson, a special education teacher for 33 years, said the brier patch in the No Child Left Behind Act is the thicket of standardized tests used to determine how schools are performing — called adequate yearly progress.

That is the yardstick by which a school is judged failing, improving or succeeding. The benchmark focuses on four racial and ethnic groups, as well as special education students. If any one of the five groups fails, the school is flagged and may be subject to reorganization, including the ouster of administrators and teachers.